Printers receive print data from a source, such as a single host computer or a network that contains at least one host computer or network server. Printers that are connected to a network can serve more than one host, and a single host computer connected to a network can access more than one printer. In a configuration where a single printer is connected to a single host computer via a parallel port, for example, the capability of the printer can be enhanced by creating a function that allows a Systems Administrator using the host computer to easily keep track of "job accounting" information involving the printer, such as the printer's paper usage per paper tray.
The printer may also be connected to more than one host computer via a network. A recent development with respect to printers is the use of an internal network adapter or other interface circuit that allows bi-directional communication with host computers. Such bi-directional communication would typically be made using a protocol known as the Network Printer Alliance Protocol (NPAP) which provides a means for returning status information from a laser printer to a host computer. The bi-directional capabilities of such laser printers, particularly Model 4039 Plus.TM. and Model Optra.TM. and ink jet printers, particularly Model 4079 Plus.TM., both types of printers being manufactured by Lexmark International, Inc., are quite broad, and can be further enhanced by creating a function that allows a Network Administrator using the host computer to easily keep track of job accounting information involving the printer, including, for example, the printer's paper usage per paper tray (as noted above). Details of the published NPAP are contained in the NPAP Specification Level 1, Revision N, dated Feb. 11, 1994. This NPAP specification is incorporated herein by reference.
Printers contain a quantity of information which would be of interest to users and Network Administrators, particularly for error conditions and other job related information, such as duration of a print job, quantity of print jobs per unit time, number of pages per job, etc. Conventional printers that are connected to a network typically have their print jobs routed through a network queue that resides on a single workstation or network server personal computer. Conventional software is available that inspects the content of the print jobs in that queue, and these programs can estimate job statistics, such as the number of pages in a particular job. Such conventional programs are prone to error, since the program is required to process the print jobs in a similar manner as an actual printer, however, the actual printer can detect operational conditions or error conditions that the software running on the network server cannot be aware of.
In addition to the above problems, some conventional printers have the ability to physically connect to more than one network simultaneously. If print statistics are to be accumulated, a queue statistics computer program that resides on each of the personal computers where a network print queue exists would be needed, so that the individual queue information can be collected for a particular personal computer. To make this information useful, all of these databases must be then merged to get the statistics for any one printer in the network. Not only is this cumbersome, but is also error prone. Furthermore, certain networks known as TCP/IP allow for printing directly to a printer, so no network queue is available to supply information to a queue statistics computer program.